Display device

ABSTRACT

A display device with a higher contrast ratio is provided. The display device is provided with stacked polarizing plates arranged displaced from a parallel nicol state. Moreover, in the display device, at least one of a pair of stacked polarizing plates is displaced from a parallel state. The pair of stacked polarizing plates is arranged in a cross nicol state. A retardation plate may be provided between the polarizing plate and the substrate. As a result, the contrast ratio can be increased.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure of a display device forenhancing a contrast ratio.

2. Description of the Related Art

A display device which is very thin and lightweight as compared to aconventional cathode-ray tube display device, a so-called flat paneldisplay, has been developed. A liquid crystal display device having aliquid crystal element as a display element, a light-emitting devicehaving a self-light-emitting element, an FED (field emission display)using an electron beam, and the like compete in the market of flat paneldisplays. Therefore, lower power consumption and a higher contrast ratioare demanded in order to increase the added value and differentiate fromother products.

In general, a liquid crystal display device is provided with onepolarizing plate over each of substrates to keep a contrast ratio. Whenblack display is performed more clearly, the contrast ratio can beimproved. Therefore, higher display quality can be provided when animage is seen in a dark room such as a home theater room.

For example, it is suggested that a first polarizing plate is providedoutside a substrate on a viewing side of a liquid crystal cell, a secondpolarizing plate is provided outside a substrate facing the substrate onthe viewing side, and a third polarizing plate is provided for enhancingthe polarization degree when light from an auxiliary light sourceprovided on the substrate side polarizes through the second polarizingplate and passes through the liquid crystal cell, in order to improve acontrast ratio and suppress unevenness of display which is caused due toshortage of the polarization degree and polarization distribution ofpolarizing plates (see Patent Document 1). [Patent Document 1] PCTInternational Publication No. 00/34821

SUMMARY OF THE INVENTION

However, a contrast ratio still has been required to be enhanced andresearches have been made for enhancement of contrast in a liquidcrystal display device. Further, it is a problem that a polarizing platehaving a high polarization degree is expensive.

In the present invention made in view of the aforementioned problem, oneof light-transmitting substrates arranged so as to face each other isprovided with stacked polarizing plates which are arranged displacedfrom a parallel nicol state.

In addition, in the present invention, both of light-transmittingsubstrates arranged so as to face each other are provided with stackedpolarizing plates. The polarizing plates that face each other areprovided in a cross nicol state, and the stacked polarizing plates arearranged displaced from a parallel nicol state. Alternatively, thepolarizing plates that face each other may be arranged displaced from across nicol state. A waveplate or a retardation plate may be providedbetween the stacked polarizing plates and the substrate.

An aspect of the present invention is a display device including: afirst light-transmitting substrate and a second light-transmittingsubstrate that face each other; a display element sandwiched between thefirst light-transmitting substrate and the second light-transmittingsubstrate; and stacked polarizing plates outside the firstlight-transmitting substrate or the second light-transmitting substrate.The stacked polarizing plates are arranged with their transmission axesdisplaced from a parallel nicol state.

Another aspect of the present invention is a display device including: afirst light-transmitting substrate and a second light-transmittingsubstrate that face each other; a display element sandwiched between thefirst light-transmitting substrate and the second light-transmittingsubstrate; first stacked polarizing plates outside the firstlight-transmitting substrate; and second stacked polarizing platesoutside the second light-transmitting substrate. The first stackedpolarizing plates are arranged with their transmission axes displacedfrom a parallel nicol state, and the second stacked polarizing platesare arranged with their transmission axes being in a parallel nicolstate.

Another aspect of the present invention is a display device including: afirst light-transmitting substrate and a second light-transmittingsubstrate that face each other; a display element sandwiched between thefirst light-transmitting substrate and the second light-transmittingsubstrate; first stacked polarizing plates outside the firstlight-transmitting substrate; and second stacked polarizing platesoutside the second light-transmitting substrate. The first stackedpolarizing plates are arranged with their transmission axes being in aparallel nicol state, and the second stacked polarizing plates arearranged with their transmission axes displaced from a parallel nicolstate.

In the present invention, the first stacked polarizing plates have thetransmission axes to be in a cross nicol state with respect to thetransmission axes of the second stacked polarizing plates.

In the present invention, the stacked polarizing plates displaced from aparallel nicol state are arranged on a viewing side.

By the simple structure in which plural polarizing plates are stackeddisplaced, the display device can have a higher contrast ratio.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B show a display device of the present invention;

FIG. 2 shows an angle between polarizing plates of the presentinvention;

FIGS. 3A and 3B show a display device of the present invention;

FIG. 4 shows an angle between polarizing plates of the presentinvention;

FIGS. 5A and 5B show a display device of the present invention;

FIG. 6 shows an angle between polarizing plates of the presentinvention;

FIGS. 7A and 7B show a display device of the present invention;

FIG. 8 shows an angle between polarizing plates of the presentinvention;

FIG. 9 is a cross-sectional view showing a display device of the presentinvention;

FIG. 10 is a cross-sectional view showing a display device of thepresent invention;

FIG. 11 is a block diagram showing a display device of the presentinvention;

FIGS. 12A to 12D each show an irradiation means of a display device ofthe present invention;

FIG. 13 shows an experiment condition of the present invention;

FIG. 14 is a graph showing an experiment result of the presentinvention;

FIG. 15 is a graph showing an experiment result of the presentinvention;

FIG. 16 is a graph showing an experiment result of the presentinvention;

FIG. 17 is a graph showing an experiment result of the presentinvention;

FIG. 18 shows an experiment condition of the present invention;

FIG. 19 is a graph showing an experiment result of the presentinvention;

FIG. 20 is a graph showing an experiment result of the presentinvention;

FIG. 21 is a graph showing an experiment result of the presentinvention;

FIG. 22 is a graph showing an experiment result of the presentinvention;

FIGS. 23A and 23B are schematic views each showing a mode of a liquidcrystal element of the present invention;

FIGS. 24A and 24B are schematic views each showing a mode of a liquidcrystal element of the present invention;

FIGS. 25A and 25B are schematic views each showing a mode of a liquidcrystal element of the present invention;

FIGS. 26A and 26B are schematic views each showing a mode of a liquidcrystal element of the present invention;

FIGS. 27A and 27B are schematic views each showing a mode of a liquidcrystal element of the present invention; and

FIGS. 28A to 28F show electronic appliances of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment Modes and Embodiments of the present invention will behereinafter described with reference to drawings. However, the presentinvention can be embodied in many different modes and it is easilyunderstood by those skilled in the art that the mode and detail can bevariously changed without departing from the scope and spirit of thepresent invention. Therefore, the present invention is not construed asbeing limited to the description of the embodiment modes andembodiments. It is to be noted that the same portions or portions havinga similar function are denoted by the same reference numeral and thedescription of such portions is not repeated.

Embodiment Mode 1

Embodiment Mode 1 will explain a concept of a display device of thepresent invention.

FIG. 1A is a cross-sectional view of a display device having a structurein which stacked polarizing plates are arranged displaced from aparallel nicol state. FIG. 1B is a perspective view of the displaydevice. This embodiment mode explains an example of a liquid crystaldisplay device having a liquid crystal element as a display element.

As shown in FIG. 1A, a layer 100 having a liquid crystal element issandwiched between a first substrate 101 and a second substrate 102which are arranged so as to face each other. Each of the substrates isan insulating substrate having a light-transmitting property(hereinafter also referred to as a light-transmitting substrate). As thesubstrates, for example, a glass substrate made of barium borosilicateglass, aluminoborosilicate glass, or the like; a quartz substrate; orthe like can be used. Further, a substrate formed of plastic typified bypolyethylene terephthalate (PET), polyethylene naphthalate (PEN), andpolyether sulfone (PES), or a synthetic resin having flexibility such asacrylic can be used as the substrates.

Stacked polarizing plates are provided outside the substrate, i.e., on aside not in contact with the layer having a liquid crystal element. Afirst polarizing plate 103 and a second polarizing plate 104 areprovided on the first substrate 101 side in such a way that the firstpolarizing plate 103 and the second polarizing plate 104 are displacedfrom a parallel nicol state.

These polarizing plates can be formed of a known material. For example,a structure where an adhesive layer, TAC (triacetylcellulose), a mixedlayer of PVA (polyvinyl alcohol) and iodine, and TAC are sequentiallystacked from the substrate side can be used. The polarization degree canbe controlled by the mixed layer of PVA (polyvinyl alcohol) and iodine.Moreover, there is a polarizing plate including an inorganic material.Further, a polarizing plate may also be referred to as a polarizing filmdue to its shape.

As shown in FIG. 1B, the first polarizing plate 103 and the secondpolarizing plate 104 are stacked in such a way that a transmission axis(A) of the first polarizing plate 103 and a transmission axis (B) of thesecond polarizing plate 104 are displaced from each other. By stackingthe polarizing plates with their transmission axes displaced in thismanner, the contrast ratio can be improved.

FIG. 2 is a top view showing an angle between the transmission axis (A)of the first polarizing plate 103 and the transmission axis (B) of thesecond polarizing plate 104. The first polarizing plate 103 and thesecond polarizing plate 104 are stacked in such a way that thetransmission axis (A) and the transmission axis (B) are displaced by anangle θ. The second polarizing plate 104 provided thus on the outer sideis stacked while being displaced.

The structure in which the stacked polarizing plates are provided overone side of the substrate as described in this embodiment mode can beapplied to a display device in which light can be extracted from oneside of the substrate.

It is to be noted that, as one feature, a polarizing plate has anabsorption axis in a direction perpendicular to a transmission axis.Therefore, a state in which the absorption axes are parallel to eachother can also be referred to as a parallel nicol state.

By arranging such stacked polarizing plates so as to displace from aparallel nicol state, light leakage in directions of the transmissionaxes can be reduced. Thus, the contrast ratio of the display device canbe enhanced.

Embodiment Mode 2

Embodiment Mode 2 will describe a concept of a display device providedwith a retardation plate in addition to stacked polarizing plates,differently from the above embodiment mode.

FIG. 3A is a cross-sectional view of a display device in which aretardation plate is provided between a substrate and polarizing platesthat are stacked displaced from a parallel nicol state. FIG. 3B is aperspective view of the display device. This embodiment mode willexplain an example of a liquid crystal display device having a liquidcrystal element as a display element.

As shown in FIG. 3A, the first polarizing plate 103 and the secondpolarizing plate 104 are provided on the first substrate 101 side. Atthis time, the first polarizing plate 103 and the second polarizingplate 104 are arranged displaced from a parallel nicol state. Moreover,a retardation plate 113 is provided between the first substrate 101 andthe stacked polarizing plates.

The retardation plate may be, for example, a film in which liquidcrystals are hybrid-oriented, a film in which liquid crystals aretwisted-oriented, a uniaxial retardation plate, or a biaxial retardationplate. Such retardation plates can widen the viewing angle of thedisplay device.

A uniaxial retardation plate is formed by stretching a resin in onedirection. Further, a biaxial retardation plate is formed by stretchinga resin into an axis in a crosswise direction, and then gentlystretching the resin into an axis in a lengthwise direction. As theresin used here, cyclo-olefin polymer (COE), polycarbonate (PC),polymethyl methacrylate (PMMA), polystyrene (PS), polyether sulfone(PES), polyphenylene sulfide (PPS), polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polypropylene (PP), polyphenylene oxide(PPO), polyarylate (PAR), polyimide (PI), polytetrafluoroethylene(PTFE), or the like is given.

Note that the film in which liquid crystals are hybrid-oriented isformed by using a triacetyl cellulose (TAC) film as a base andhybrid-aligning discotic liquid crystals or nematic liquid crystals. Theretardation plate can be attached to a light-transmitting substrateafter being attached to a polarizing plate.

In this embodiment mode, a reflective plate may be added. The reflectiveplate can be provided outside the second substrate 102 or can beobtained by forming a pixel electrode with a highly reflective material.

As shown in FIG. 3B, the first polarizing plate 103 and the secondpolarizing plate 104 are stacked in such a way that the transmissionaxis (A) of the first polarizing plate 103 and the transmission axis (B)of the second polarizing plate 104 are displaced from each other. Morespecifically, the transmission axis (A) of the first polarizing plate103 and a slow axis (E) of the retardation plate 113 are displaced by45° from each other. By providing the retardation plate in this manner,black display can be performed and the viewing angle can be made wider.An angle of 45° is just an example, and other predetermined angles maybe set as long as the viewing angle can be wider. In this manner, whenthe polarizing plates are stacked with their transmission axes displacedfrom each other and the retardation plate is provided, the contrastratio can be improved.

FIG. 4 is a top view showing angles among the transmission axis (A) ofthe first polarizing plate 103, the transmission axis (B) of the secondpolarizing plate 104, and the slow axis (E) of the retardation plate113. The first polarizing plate 103 and the second polarizing plate 104are stacked in such a way that the transmission axis (A) and thetransmission axis (B) are displaced by an angle θ. In addition, thefirst polarizing plate 103 and the retardation plate 113 are arranged insuch a way that the transmission axis (A) and the slow axis (E) have anangle of 45° therebetween.

The structure having the stacked polarizing plates over one side of thesubstrate as described in this embodiment mode can be applied to adisplay device in which light can be extracted from one side of thesubstrate.

It is to be noted that, as one feature, a retardation plate has a fastaxis in a direction perpendicular to a slow axis. Therefore, thearrangement can be decided based on the fast axis instead of the slowaxis.

In this manner, when the polarizing plates are stacked so as to displacefrom a parallel nicol state and the retardation plate is furtherprovided, light leakage in directions of the transmission axes can bereduced. Accordingly, the contrast ratio of the display device can beimproved.

Embodiment Mode 3

Differently from the above embodiment mode, Embodiment Mode 3 willdescribe a concept of a display device provided with a pair of stackedpolarizing plates.

FIG. 5A is a cross-sectional view showing a display device with astructure in which a pair of stacked polarizing plates is provided andat least one of the pair of stacked polarizing plates is arrangeddisplaced from a parallel nicol state. FIG. 5B is a perspective view ofthe display device. This embodiment mode will explain an example of aliquid crystal display device having a liquid crystal element as adisplay element.

In this embodiment mode, stacked polarizing plates are provided outsidethe substrate, i.e., on a side not in contact with a layer having aliquid crystal element. Specifically, as shown in FIG, 5A, the firstpolarizing plate 103 and the second polarizing plate 104 are provided inorder on the first substrate 101 side. A third polarizing plate 105 anda fourth polarizing plate 106 are provided in order on the secondsubstrate 102 side. In this embodiment mode, at least one of the pair ofstacked polarizing plates is displaced from a parallel nicol state. Inspecific, as shown in FIG. 5B, the first polarizing plate 103 and thesecond polarizing plate 104 are stacked in such a way that thetransmission axis (A) and the transmission axis (B) are displaced from aparallel state. Then, the third polarizing plate 105 and the fourthpolarizing plate 106 are stacked in such a way that a transmission axis(C) of the third polarizing plate 105 and a transmission axis (D) of thefourth polarizing plate 106 are in a parallel state, i.e., a parallelnicol state.

Then, the first polarizing plate 103 and the third polarizing plate 105are arranged so as to be in a cross nicol state. That is to say, thethird and fourth polarizing plates that are stacked and the firstpolarizing plate are arranged so as to be in a cross nicol state, andthe second polarizing plate is arranged displaced from the firstpolarizing plate. The polarizing plate to be displaced is preferably thepolarizing plate that is arranged on an outer side among the stackedpolarizing plates.

It is to be noted that the first polarizing plate 103 and the thirdpolarizing plate 105 may be displaced from a cross nicol state withinthe range of obtaining predetermined black display.

The transmission axis (B) of the second polarizing plate 104 isdisplaced so as to correspond to a minor-axis direction of an ellipse ofelliptically-polarized light emitted from the first polarizing plate103. That is to say, an absorption axis of the second polarizing plate104 is displaced so as to correspond to a major-axis direction of anellipse of elliptically-polarized light emitted from the firstpolarizing plate 103.

Although not shown in FIGS. 5A and 5B, an irradiation means such as abacklight is provided under the fourth polarizing plate 106. That is,the polarizing plate to be displaced is preferably the polarizing platethat is arranged on an outer side among the stacked polarizing plates ona viewing side to which the irradiation means is not provided.

FIG. 6 is a top view showing angles among the transmission axis (A) ofthe first polarizing plate 103, the transmission axis (B) of the secondpolarizing plate 104, the transmission axis (C) of the third polarizingplate 105, and the transmission axis (D) of the fourth polarizing plate106. The first polarizing plate 103 and the second polarizing plate 104are stacked in such a way that the transmission axis (A) and thetransmission axis (B) are displaced by an angle θ. In this embodimentmode, the third polarizing plate 105 and the fourth polarizing plate 106are arranged in such a way that the transmission axis (C) and thetransmission axis (D) are in a parallel nicol state.

As shown in this embodiment mode, the pair of stacked polarizing platescan be applied to a display device in which light can be extracted froma side opposite to the substrate provided with the backlight. Inaddition, the pair of stacked polarizing plates may be applied to adisplay device in which, by using a light-transmitting backlight, lightcan be extracted also from the substrate provided with the backlight,i.e., a display device in which light can be extracted from both sides.

In this manner, when at least one of the pair of stacked polarizingplates, preferably stacked polarizing plates on the viewing side, isprovided so that the transmission axes are displaced from a parallelnicol state, light leakage in directions of the transmission axes can bereduced. Therefore, the contrast ratio of the display device can beimproved.

Embodiment Mode 4

This embodiment mode will explain a mode of stacked polarizing platesthat are displaced differently from the above embodiment mode.

Although the above embodiment mode shows that the first polarizing plate103 and the third polarizing plate 105 are arranged so as to be in across nicol state, the present invention is not limited to this. Forexample, the third polarizing plate 105 and the first and secondpolarizing plates 103 and 104 may be arranged displaced from a crossnicol state, and the first polarizing plate 103 and the secondpolarizing plate 104 may be arranged so as to be in a parallel nicolstate.

In this case, the transmission axis (A) of the first polarizing plate103 is displaced in a minor-axis direction of an ellipse ofelliptically-polarized light emitted from a liquid crystal element.Concerning an absorption axis, it can be said that an absorption axis ofthe first polarizing plate 103 is displaced in a major-axis direction ofan ellipse of elliptically-polarized light emitted from a liquid crystalelement.

The contrast ratio can be improved also by displacing the pair ofstacked polarizing plates from a cross nicol state.

Embodiment Mode 5

This embodiment mode will explain a concept of a display device providedwith a retardation plate in addition to a pair of stacked polarizingplates, differently from the above embodiment mode.

FIG. 7A is a cross-sectional view of a display device in which one of apair of stacked polarizing plates is displaced from a parallel nicolstate, and each retardation plate is provided between a substrate andone of the pair of polarizing plates. This embodiment mode explains anexample of a liquid crystal display device having a liquid crystalelement as a display element.

As shown in FIG. 7A, the first polarizing plate 103 and the secondpolarizing plate 104 are provided on the first substrate 101 side. Thethird polarizing plate 105 and the fourth polarizing plate 106 areprovided on the second substrate 102 side.

As shown in FIG. 7B, the first polarizing plate 103 and the secondpolarizing plate 104 are arranged displaced from a parallel nicol state.The retardation plate 113 is provided between the first substrate 101and the stacked polarizing plates.

Moreover, as shown in FIG. 7B, the third polarizing plate 105 and thefourth polarizing plate 106 are provided on the second substrate 102side. The third polarizing plate 105 and the fourth polarizing plate 106are arranged so as to be in a parallel nicol state. In addition, aretardation plate 114 is provided between the second substrate 102 andthe stacked polarizing plates.

Although not shown in FIGS. 7A and 7B, an irradiation means such as abacklight is provided under the fourth polarizing plate 106.

In this embodiment mode, the first polarizing plate 103 and the thirdpolarizing plate 105 are arranged so as to be in a cross nicol state.The first polarizing plate 103 and the third polarizing plate 105 may bedisplaced from a cross nicol state within the range of obtainingpredetermined black display.

FIG. 8 is a top view showing angles among the transmission axis (A) ofthe first polarizing plate 103, the transmission axis (B) of the secondpolarizing plate 104, the transmission axis (C) of the third polarizingplate 105, and the transmission axis (D) of the fourth polarizing plate106. The first polarizing plate 103 and the second polarizing plate 104are stacked in such a way that the transmission axis (A) and thetransmission axis (B) are displaced by an angle θ. The transmission axis(B) of the second polarizing plate 104 is displaced so as to correspondto a minor-axis direction of an ellipse of elliptically-polarized lightemitted from the transmission axis (A) of the first polarizing plate103. This displacement angle corresponds to 74. In this embodiment mode,the third polarizing plate 105 and the fourth polarizing plate 106 arearranged in such a way that the transmission axis (C) and thetransmission axis (D) are in a parallel nicol state. The firstpolarizing plate 103 and the third polarizing plate 105 are arranged insuch a way that the transmission axis (A) and the transmission axis (C)are in a cross nicol state.

As shown in this embodiment mode, the pair of stacked polarizing platescan be applied to the display device in which light can be extractedfrom both sides of the substrate.

In the structure having the pair of stacked polarizing plates and theretardation plates in this manner, light leakage in directions of thetransmission axes can be reduced by stacking the polarizing plates so asto displace from a parallel nicol state on at least one side, preferablyon a viewing side. Accordingly, the contrast ratio of the display devicecan be improved.

Embodiment Mode 6

Embodiment Mode 6 will describe a mode having a retardation plate andpolarizing plates which are stacked displaced differently from the aboveembodiment mode.

Although the above embodiment mode shows the mode in which theretardation plate is provided and the first polarizing plate 103 and thethird polarizing plate 105 are arranged so as to be in a cross nicolstate, the present invention is not limited to this. For example, thestructure may be that the retardation plate is provided, the thirdpolarizing plate 105 and the first and second polarizing plates 103 and104 are arranged displaced from a cross nicol state, and the firstpolarizing plate 103 and the second polarizing plate 104 are arranged ina parallel nicol state.

In this case, the transmission axis (A) of the first polarizing plate103 is displaced in a minor-axis direction of an ellipse ofelliptically-polarized light emitted from a liquid crystal element.Concerning an absorption axis, it can be said that the absorption axisof the first polarizing plate 103 is displaced in a major-axis directionof an ellipse of elliptically-polarized light emitted from the liquidcrystal element.

The contrast ratio can also be improved by having the retardation plateand displacing the pair of stacked polarizing plates from a cross nicolstate.

Embodiment Mode 7

Embodiment Mode 7 will describe a structure of a liquid crystal displaydevice having a structure in which a pair of stacked polarizing platesis provided and transmission axes of at least one of the pair of stackedpolarizing plates are displaced from each other.

FIG. 9 is a cross-sectional view of a liquid crystal display devicehaving stacked polarizing plates.

The liquid crystal display device includes a pixel portion 205 and adriving circuit portion 208. In the pixel portion 205 and the drivingcircuit portion 208, a base film 302 is provided over a substrate 301.An insulating substrate similar to any of those in the aforementionedembodiment mode can be used as the substrate 301. It is concerned that asubstrate formed of a synthetic resin generally has lower heatresistance than other substrates; however, it can be employed bytransferring an element to a substrate formed of a synthetic resin aftermanufacturing the element using a substrate with higher heat resistance.

The pixel portion 205 is provided with a transistor as a switchingelement with the base film 302 interposed therebetween. In thisembodiment mode, a thin film transistor (TFT) is used as the transistor,which is referred to as a switching TFT 303. A TFT can be formed by manymethods. For example, a crystalline semiconductor film is used as anactive layer. A gate electrode is provided over the crystallinesemiconductor film with a gate insulating film interposed therebetween.An impurity element can be added to the active layer by using the gateelectrode. When an impurity element is added using the gate electrode inthis manner, a mask for adding the impurity element is not necessary.The gate electrode may have a single-layer structure or a stacked-layerstructure. An impurity region can be formed as a high-concentrationimpurity region or a low-concentration impurity region by controllingthe concentration thereof. A structure of a TFT thus having alow-concentration impurity region is referred to as an LDD(Lightly-Doped Drain) structure. The low-concentration impurity regioncan be formed so as to overlap with the gate electrode. A structure ofsuch a TFT is referred to as a GOLD (Gate Overlapped LDD) structure.FIG. 9 shows the switching TFT 303 having a GOLD structure. The polarityof the switching TFT 303 is an n-type by using phosphorus (P) or thelike for an impurity region thereof. In the case of forming a p-typeTFT, boron (B) or the like may be added. After that, a protective filmcovering a gate electrode and the like is formed. A dangling bond in thecrystalline semiconductor film can be terminated by hydrogen elementsmixed in the protective film. Further, in order to enhance the flatness,an interlayer insulating film 305 may be formed. The interlayerinsulating film 305 may be formed of an organic material or an inorganicmaterial, or formed using a stacked-layer structure of these. Openingsare formed in the interlayer insulating film 305, the protective film,and the gate insulating film; thereby wirings connected to the impurityregions are formed. In this manner, the switching TFT 303 can be formed.It is to be noted that the present invention is not limited to thestructure of the switching TFT 303.

Then, a pixel electrode 306 connected to the wiring is formed.

Further, a capacitor 304 can be formed at the same time as the switchingTFT 303. In this embodiment mode, the capacitor 304 is formed of a stackof a conductive film formed at the same time as the gate electrode, theprotective film, the interlayer insulating film 305, and the pixelelectrode 306.

Further, a pixel portion and a driving circuit portion can be formedover one substrate by using a crystalline semiconductor film. In thatcase, transistors in the pixel portion and transistors in the drivingcircuit portion 208 are formed at the same time. The transistors usedfor the driving circuit portion 208 form a CMOS circuit; therefore, thetransistors are referred to as a CMOS circuit 354. Each of the TFTs thatform the CMOS circuit 354 may have a similar structure to the switchingTFT 303. Further, the LDD structure can be used instead of the GOLDstructure, and a similar structure is not necessarily required.

An alignment film 308 is formed so as to cover the pixel electrode 306.The alignment film 308 is subjected to rubbing treatment. This rubbingtreatment is not performed in some cases in a specific mode of a liquidcrystal, for example, in a case of a VA mode.

Next, a counter substrate 320 is provided. A color filter 322 and ablack matrix (BM) 324 can be provided inside the counter substrate 320,that is, on the side which is in contact with a liquid crystal. Thesecan be formed by known methods; however, a droplet discharging method(representatively an ink-jetting method) by which a predeterminedmaterial is dropped can eliminate the waste of the material. Further,the color filter 322 and the like are provided in a region where theswitching TFT 303 is not provided. That is to say, the color filter 322is provided so as to face a light-transmitting region, i.e., an openingregion. It is to be noted that the color filter and the like may beformed of materials which exhibit red (R), green (G), and blue (B) inthe case where a liquid crystal display device performs full-colordisplay, and a material which exhibits at least one color in the case ofmono-color display.

It is to be noted that the color filter is not provided in some caseswhen diodes (LEDs) of RGB and the like are arranged in a backlight and asuccessive additive color mixing method (field sequential method) inwhich color display is performed by time division. The black matrix 324is provided to reduce reflection of external light due to the wiring ofthe switching TFT 303 and the CMOS circuit 354. Therefore, the blackmatrix 324 is provided so as to overlap with the switching TFT 303 andthe CMOS circuit 354. Note that the black matrix 324 may be provided soas to overlap with the capacitor 304. Accordingly, reflection by a metalfilm included in the capacitor 304 can be prevented.

Then, the counter electrode 323 and an alignment film 326 are provided.The alignment film 308 and the alignment film 326 are subjected torubbing treatment. This rubbing treatment is not performed in some casesin a specific mode of a liquid crystal, for example, in a case of a VAmode.

It is to be noted that the wiring included in the TFT, the gateelectrode, the pixel electrode 306, and the counter electrode 323 can beselected from indium tin oxide (ITO), indium zinc oxide (IZO) in whichzinc oxide (ZnO) is mixed in indium oxide, a conductive material inwhich silicon oxide (SiO₂) is mixed in indium oxide, organic indium,organotin, a metal such as tungsten (W), molybdenum (Mo), zirconium(Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium(Cr), cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt), aluminum(Al), or copper (Cu), an alloy thereof, and metal nitride thereof.

Such a counter substrate 320 is attached to the substrate 301 by using asealing material 328. The sealing material 328 can be drawn over thesubstrate 301 or the counter substrate 320 by using a dispenser or thelike. Further, a spacer 325 is provided in a part of the pixel portion205 and the driving circuit portion 208 in order to hold a space betweenthe substrate 301 and the counter substrate 320. The spacer 325 has acolumnar shape, a spherical shape, or the like.

A liquid crystal 311 is injected between the substrate 301 and thecounter substrate 320 attached to each other in this manner. It ispreferable to inject the liquid crystal in vacuum. The liquid crystal311 can be formed by a method other than an injecting method. Forexample, the liquid crystal 311 may be dropped and then the countersubstrate 320 may be attached. Such a dropping method is preferablyemployed when using a large substrate to which the injecting methodcannot be applied easily.

The liquid crystal 311 includes a liquid crystal molecule of which tiltis controlled by the pixel electrode 306 and the counter electrode 323.Specifically, the tilt of the liquid crystal molecule is controlled by avoltage applied to the pixel electrode 306 and the counter electrode323. Such a control is performed using a control circuit provided in thedriving circuit portion 208. It is to be noted that the control circuitis not necessarily formed over the substrate 301 and a circuit connectedthrough a connecting terminal 310 may be used. In this case, ananisotropic conductive film containing conductive microparticles can beused so as to be connected to the connecting terminal 310. Further, thecounter electrode 323 is electrically connected to a part of theconnecting terminal 310, whereby a potential of the counter electrode323 can be common. For example, a bump 337 can be used for theconduction.

Next, description is made of a structure of a backlight unit 352. Thebacklight unit 352 includes a cold cathode tube, a hot cathode tube, adiode, an inorganic EL element, or an organic EL element as a lightsource 331 which emits fluorescence, a lamp reflector 332 to effectivelylead fluorescence to a light guide plate 335, the light guide plate 335by which fluorescence is totally reflected and led to the entiresurface, a diffusing plate 336 for reducing variation in brightness, anda reflective plate 334 for reusing light leaking under the light guideplate 335.

A control circuit for controlling the luminance of the light source 331is connected to the backlight unit 352. The luminance of the lightsource 331 can be controlled by a signal supplied from the controlcircuit.

Further, polarizing plates 315 and 316 that are stacked are providedbetween the substrate 301 and the backlight unit 352 and polarizingplates 313 and 314 that are stacked are provided over the countersubstrate 320 as well. The polarizing plate 315 and the polarizing plate316 provided on the backlight side are arranged so as to be in aparallel nicol state, and the polarizing plate 313 and the polarizingplate 314 provided on a viewing side are arranged displaced from aparallel nicol state. In the present invention, one of the pair ofstacked polarizing plates, preferably one on the viewing side, has thetransmission axes displaced from each other. Accordingly, the contrastratio can be improved.

The stacked polarizing plates 315 and 316, and the stacked polarizingplates 313 and 314 are attached to the substrate 301 and the countersubstrate 320, respectively. A retardation plate may be provided betweenthe stacked polarizing plates and the substrate.

The contrast ratio can be improved by arranging the stacked polarizingplates with their transmission axes displaced in such a liquid crystaldisplay device. By displacing the stacked polarizing plates, thecontrast ratio can be made higher than that in a structure in which thefilm thickness of the polarizing plate of a single-layer structure issimply increased.

This embodiment mode can be freely combined with the above embodimentmode.

Embodiment Mode 8

In this embodiment mode, description is made of a liquid crystal displaydevice which has a polarizing plate having a stacked-layer structure anduses a TFT having an amorphous semiconductor film, differently from theaforementioned embodiment modes.

FIG. 10 shows a structure of a liquid crystal display device including atransistor using an amorphous semiconductor film for a switching element(hereinafter referred to as an amorphous TFT). The pixel portion 205 isprovided with the switching TFT 303 formed using an amorphous TFT. Theamorphous TFT can be formed by a known method. For example, in the caseof a channel-etch type, a gate electrode is formed over the base film302; a gate insulating film is formed so as to cover the gate electrode;and then, an n-type semiconductor film, an amorphous semiconductor film,a source electrode, and a drain electrode are formed. An opening isformed in the n-type semiconductor film by using the source electrodeand the drain electrode. A part of the amorphous semiconductor film isalso removed in this case; therefore, this TFT is referred to as achannel-etch type. After that, a protective film 307 is formed, wherebythe amorphous TFT can be formed. Further, there is also a channelprotective type amorphous TFT where a protective film is provided sothat an amorphous semiconductor film is not removed when forming anopening in the n-type semiconductor film by using the source electrodeand the drain electrode. Other structures may be formed similarly to thechannel-etch type.

Subsequently, the alignment film 308 is formed similarly to FIG. 9, andthen rubbing treatment is performed. This rubbing treatment is notperformed in some cases in a specific mode of a liquid crystal, forexample, in a case of a VA mode.

Further, the counter substrate 320 is provided similarly to FIG. 9 andattached by using the sealing material 328. By injecting the liquidcrystal 311 between them, a liquid crystal display device can be formed.

Similarly to FIG. 9, the stacked polarizing plates 315 and 316 areprovided between the substrate 301 and the backlight unit 352, and thestacked polarizing plates 313 and 314 are provided over the countersubstrate 320 as well. The polarizing plates 315 and 316 on thebacklight side are provided so as to be in a parallel nicol state andthe polarizing plates 313 and 314 on the viewing side are arrangeddisplaced from a parallel nicol state. In the present invention, one ofthe pair of stacked polarizing plates, preferably one on the viewingside, has the transmission axes displaced from each other. Accordingly,the contrast ratio can be improved.

The stacked polarizing plates 315 and 316 and the stacked polarizingplates 313 and 314 are attached to the substrate 301 and the countersubstrate 320, respectively. In addition, a retardation plate may beprovided between the stacked polarizing plates and the substrate.

In the case of forming a liquid crystal display device by using anamorphous TFT as the switching TFT 303, an IC 421 formed using a siliconwafer can be mounted as a driver on the driving circuit portion 208 inconsideration of operating performance. For example, a signal to controlthe switching TFT 303 can be supplied by connecting a wiring of the IC421 and a wiring connected to the switching TFT 303 by using ananisotropic conductor having a conductive microparticle 422. It is to benoted that a mounting method of the IC is not limited to this and the ICmay be mounted by a wire bonding method.

Further, the IC can be connected to a control circuit with theconnecting terminal 310 interposed therebetween. At this time, ananisotropic conductive film having the conductive microparticle 422 canbe used to connect the IC to the connecting terminal 310.

Since other structures are similar to FIG. 9, description thereof isomitted here.

The contrast ratio can be improved by arranging the stacked polarizingplates with their transmission axes displaced in such a liquid crystaldisplay device. In the present invention, plural polarizing plates arepolarizing plates having a stacked layer structure arranged so thattheir transmission axes are displaced from each other; therefore, thepresent invention is different from a structure in which the filmthickness of the polarizing plate with a single-layer structure issimply increased. Compared with the structure in which the filmthickness of the polarizing plate is increased, the present invention ispreferable because the contrast ratio can be higher.

This embodiment mode can be freely combined with the above embodimentmode.

Embodiment Mode 9

In this embodiment mode, description is made of an operation of eachcircuit or the like included in a liquid crystal display device.

FIG. 11 is a system block diagram showing a pixel portion 700 and adriving circuit portion of a liquid crystal display device.

In the pixel portion 700, a plurality of pixels are included and aswitching element is provided in an intersecting region of a signal line212 and a scan line 210 which will become each pixel. Application of avoltage to control tilt of a liquid crystal molecule can be controlledby the switching element. Such a structure where a switching element isprovided in each intersecting region is referred to as an active type.The pixel portion of the present invention is not limited to such anactive type, and may have a passive type structure. The passive type canbe formed by a simple process since each pixel does not have a switchingelement.

The driving circuit portion 208 includes a control circuit, a signalline driving circuit 722, a scan line driving circuit 723, and the like.The control circuit has a function to control a gray scale in accordancewith a display content of the pixel portion 700. Therefore, the controlcircuit inputs a generated signal to the signal line driving circuit 722and the scan line driving circuit 723. When a switching element isselected through the scan line 210 in accordance with the scan linedriving circuit 723, a voltage is applied to a pixel electrode in aselected intersecting region. The value of this voltage is determinedbased on a signal inputted from the signal line driving circuit 722through the signal line.

Further, in the control circuit, a signal to control power supplied to alighting means is generated, and the signal is inputted to a powersource of the lighting means. The backlight unit described in theaforementioned embodiment mode can be used for the lighting means. Notethat the lighting means includes a front light besides a backlight. Afront light is a platy light unit formed of an illuminant and a lightguiding body, which is attached to a front side of a pixel portion andilluminates the whole place. By such a lighting means, the pixel portioncan be evenly illuminated with low power consumption.

Further, as shown in FIG. 11, the scan line driving circuit 723 includescircuits which function as a shift register 701, a level shifter 704,and a buffer 705. Signals such as a gate start pulse (GSP) and a gateclock signal (GCK) are inputted to the shift register 701. It is to benoted that the scan line driving circuit of the present invention is notlimited to the structure shown in FIG. 11.

Further, as shown in FIG. 11, the signal line driving circuit 722includes circuits which function as a shift register 711, a first latch712, a second latch 713, a level shifter 714, and a buffer 715. Thecircuit functioning as the buffer 715 is a circuit having a function toamplify a weak signal and includes an operational amplifier and thelike. Signals such as start pulses (SSP) are inputted to the levelshifter 714, and data (DATA) of a video signal and the like is inputtedto the first latch 712. Latch (LAT) signals can be temporarily held inthe second latch 713, and are inputted to the pixel portion 700concurrently. This operation is referred to as line sequential drive.Therefore, a pixel which performs not line sequential drive but dotsequential drive does not require the second latch. Thus, the signalline driving circuit of the present invention is not limited to thestructure shown in FIG. 11.

The signal line driving circuit 722, the scan line driving circuit 723,and the pixel portion 700 as described above can be formed ofsemiconductor elements provided over one substrate. For example, thesemiconductor element can be formed using a thin film transistorprovided over a glass substrate. In this case, a crystallinesemiconductor film is preferably applied to a semiconductor element (seeEmbodiment Mode 5). A crystalline semiconductor film can be used to forma circuit included in a driving circuit portion since it has highelectrical characteristics, in particular, mobility. Further, the signalline driving circuit 722 and the scan line driving circuit 723 may bemounted on a substrate by using an IC (Integrated Circuit) chip. In thiscase, an amorphous semiconductor film can be applied to a semiconductorelement in a pixel portion (see Embodiment Mode 6).

The contrast ratio can be improved by arranging the stacked polarizingplates with their transmission axes displaced in such a liquid crystaldisplay device.

This embodiment mode can be freely combined with the above embodimentmode.

Embodiment Mode 10

In this embodiment mode, a structure of a backlight is described. Abacklight is provided in a display device as a backlight unit having alight source, and the light source of the backlight unit is surroundedby a reflection plate for scattering light efficiently.

As shown in FIG. 12A, a cold cathode tube 401 can be used as a lightsource of the backlight unit 352. In addition, the lamp reflector 332can be provided to reflect light from the cold cathode tube 401efficiently. The cold cathode tube 401 is often used for a large displaydevice for intensity of luminance of light from the cold cathode tube.Therefore, such a backlight unit having a cold cathode tube can be usedfor a display of a personal computer.

As shown in FIG. 12B, a diode (LED) can be used as light sources of thebacklight unit 352. For example, diodes (W) 402 which emit white lightare provided at predetermined intervals. In addition, the lamp reflector332 can be provided to reflect light from the diodes (W) 402efficiently.

As shown in FIG. 12C, diodes (LEDs) 403, 404, and 405 of RGB colors canbe used as light sources of the backlight unit 352. By using the diodes(LEDs) 403, 404, and 405 of RGB colors, higher color reproducibility canbe realized in comparison with a case of using only the diodes (W) 402which emit white light. In addition, the lamp reflector 332 can beprovided to reflect light from the diodes (W) 402 efficiently.

Further, as shown in FIG. 12D, in the case where the diodes (LEDs) 403,404, and 405 of RGB colors are used as light sources, the number andarrangement of them are not necessarily the same. For example, aplurality of diodes of a color having low emission intensity (forexample, green) may be arranged.

Further, the diode (W) 402 which emits white light may be used incombination with the diodes (LED) 403, 404, and 405 of RGB colors.

Note that in the case of having the diodes of RGB colors, the diodes aresequentially lighted in accordance with time by applying a fieldsequential mode, whereby color display can be performed.

Using a diode is suitable for a large display device since the luminanceis high. Further, since the color purity of RGB colors is high, a diodehas excellent color reproducibility as compared to a cold cathode tube.In addition, an area required for arrangement can be reduced; therefore,a narrower frame can be achieved when a diode is applied to a smalldisplay device.

Further, a light source is not necessarily provided as the backlightunit shown in FIGS. 12A to 12D. For example, in the case where abacklight having a diode is mounted on a large display device, the diodecan be arranged on a back side of the substrate. In this case, thediodes of RGB colors can be sequentially arranged at predeterminedintervals. Depending on arrangement of the diodes, color reproducibilitycan be enhanced.

Stacked polarizing plates are arranged with their transmission axesdisplaced in such a display device using a backlight, whereby an imagewith a high contrast ratio can be produced. In particular, a backlighthaving a diode is suitable for a large display device. By increasing theluminance of white display of a large display device, a high-qualityimage can be produced even in a dark place.

This embodiment mode can be freely combined with the above embodimentmode.

Embodiment Mode 11

Driving methods of a liquid crystal of a liquid crystal display deviceinclude a vertical electric field method where a voltage is appliedperpendicular to a substrate and a horizontal electric field methodwhere a voltage is applied in parallel to a substrate. Either thevertical electric field method or the horizontal electric field methodcan be applied to a structure in which polarizing plates are arrangedwith their transmission axes displaced. In this embodiment mode,description is made of various liquid crystal modes to which stackedpolarizing plates arranged with their transmission axes displaced can beapplied.

First, FIGS. 23A and 23B are pattern diagrams each showing a liquidcrystal display device of a TN mode.

In a similar manner to the above embodiment mode, the layer 100 having adisplay element is sandwiched between the first substrate 101 and thesecond substrate 102 that are provided so as to face each other. On thefirst substrate 101 side, the first polarizing plate 103 and the secondpolarizing plate 104 are arranged displaced from a parallel nicol state.Meanwhile, on the second substrate 102 side, the third polarizing plate105 and the fourth polarizing plate 106 are arranged so as to be in aparallel nicol state. It is to be noted that the first polarizing plate103 and the third polarizing plate 105 are arranged so as to be in across nicol state.

Although not shown, a backlight and the like are provided outside thefourth polarizing plate 106. A first electrode 108 and a secondelectrode 109 are provided over the first substrate 101 and the secondsubstrate 102, respectively. In addition, an electrode on the sideopposite to the backlight, that is, an electrode on the viewing side,such as the first electrode 108, is formed so as to have at least alight-transmitting property.

In the case where a liquid crystal display device having such astructure is in a normally white mode, when a voltage is applied to thefirst electrode 108 and the second electrode 109 (referred to as avertical electric field method), black display is performed as shown inFIG. 23A. At that time, liquid crystal molecules are aligned vertically.Thus, light from the backlight cannot pass through the substrate, whichleads to black display.

Then, when a voltage is not applied between the first electrode 108 andthe second electrode 109 as shown in FIG. 23B, white display isperformed. At this time, liquid crystal molecules are alignedhorizontally and are in a twisted state in a plane. Accordingly, lightfrom the backlight can pass through the substrate over which one of apair of polarizing plates, which is stacked on the viewing side, isprovided displaced from a parallel nicol state; therefore, apredetermined image can be displayed.

By providing a color filter at that time, full-color display can beperformed. The color filter can be provided on either the firstsubstrate 101 side or the second substrate 102 side.

A known liquid crystal material may be used for a TN mode.

FIGS. 24A and 24B are pattern diagrams each showing a liquid crystaldisplay device of a VA mode. A VA mode is a mode where liquid crystalmolecules are aligned perpendicularly to a substrate when there is noelectric field.

Similarly to FIGS. 23A and 23B, the first electrode 108 and the secondelectrode 109 are provided over the first substrate 101 and the secondsubstrate 102, respectively. In addition, an electrode on the sideopposite to the backlight, that is, an electrode on the viewing side,such as the first electrode 108, is formed so as to have at least alight-transmitting property. The first polarizing plate 103 and thesecond polarizing plate 104 are arranged displaced from a parallel nicolstate. On the second substrate 102 side, the third polarizing plate 105and the fourth polarizing plate 106 are arranged so as to be in aparallel nicol state. The first polarizing plate 103 and the thirdpolarizing plate 105 are arranged so as to be in a cross nicol state.

When a voltage is applied to the first electrode 108 and the secondelectrode 109 (vertical electric field method) in a liquid crystaldisplay device having such a structure, white display is performed,which means an on state, as shown in FIG. 24A. At that time, liquidcrystal molecules are aligned horizontally. Thus, light from thebacklight can pass through the substrate provided with the stackedpolarizing plates arranged displaced from a parallel nicol state,whereby a predetermined image is displayed. By providing a color filterat that time, full-color display can be performed. The color filter canbe provided on either the first substrate 101 side or the secondsubstrate 102 side.

As shown in FIG. 24B, when a voltage is not applied between the firstelectrode 108 and the second electrode 109, black display is performed,which means an off state. At that time, liquid crystal molecules arealigned vertically. Thus, light from the backlight cannot pass throughthe substrate, which leads to black display.

Thus, in an off state, liquid crystal molecules rise to be perpendicularto a substrate, whereby black display is performed. Meanwhile, in an onstate, liquid crystal molecules lie down to be parallel to a substrate,whereby white display is performed. In an off state, liquid crystalmolecules rise; therefore, polarized light from the backlight passesthrough a cell without being affected by the liquid crystal molecules,and can be completely blocked by the polarizing plates on a countersubstrate side. Accordingly, further enhancement of contrast isanticipated by providing a pair of stacked polarizing plates in such away that at least one of the pair of stacked polarizing plates isarranged displaced from a parallel nicol state.

Moreover, the stacked polarizing plates of the present invention can beapplied to an MVA (Multi-domain Vertical Alignment) mode in which thealignment of liquid crystal molecules is divided.

A known liquid crystal material may be used for a VA (VerticalAlignment) mode or an MVA mode.

FIGS. 25A and 25B are pattern diagrams each showing a liquid crystaldisplay device of an OCB (Optical Compensated Bend) mode. In the OCBmode, alignment of liquid crystal molecules forms a compensation stateoptically in a liquid crystal layer, which is referred to as bendalignment.

Similarly to FIGS. 23A and 23B, the first electrode 108 and the secondelectrode 109 are provided over the first substrate 101 and the secondsubstrate 102, respectively. Moreover, although not shown, the backlightand the like are provided outside the fourth polarizing plate 106. Inaddition, an electrode on the side opposite to the backlight, that is,an electrode on the viewing side, such as the first electrode 108, isformed so as to have at least a light-transmitting property. The firstpolarizing plate 103 and the second polarizing plate 104 are arrangeddisplaced from a parallel nicol state. The third polarizing plate 105and the fourth polarizing plate 106 are arranged so as to be in aparallel nicol state on the second substrate 102 side. The firstpolarizing plate 103 and the third polarizing plate 105 are arranged soas to be in a cross nicol state.

When a voltage is applied to the first electrode 108 and the secondelectrode 109 (vertical electric field method) in a liquid crystaldisplay device having such a structure, black display is performed asshown in FIG. 25A. At that time, liquid crystal molecules are alignedvertically. Thus, light from the backlight cannot pass through thesubstrate, which leads to black display.

When a voltage is not applied between the first electrode 108 and thesecond electrode 109, white display is performed as shown in FIG. 25B.At that time, liquid crystal molecules are aligned tilted. Thus, lightfrom the backlight can pass through the substrate provided with thestacked polarizing plates, whereby a predetermined image is displayed.By providing a color filter at that time, full-color display can beperformed. The color filter can be provided on either the firstsubstrate 101 side or the second substrate 102 side.

In such an OCB mode, birefringence caused in a liquid crystal layer canbe compensated by providing a pair of stacked polarizing plates in sucha way that one of the pair of stacked polarizing plates on the viewingside is arranged displaced from a parallel nicol state. Accordingly, awider viewing angle can be realized, and a contrast ratio can beenhanced.

FIGS. 26A and 26B are pattern diagrams each showing a liquid crystaldisplay device of an IPS (In-Plane Switching) mode. In the IPS mode,liquid crystal molecules are twisted normally in a plane with respect toa substrate, and a horizontal electric field method where electrodes areprovided on one substrate side is employed.

In the IPS mode, a liquid crystal is controlled by a pair of electrodesprovided over one substrate. Therefore, a pair of electrodes 111 and 112is provided over the second substrate 102. The pair of electrodes 111and 112 preferably has a light-transmitting property. The firstpolarizing plate 103 and the second polarizing plate 104 are arrangeddisplaced from a parallel nicol state. On the second substrate 102 side,the third polarizing plate 105 and the fourth polarizing plate 106 arearranged so as to be in a parallel nicol state. The first polarizingplate 103 and the third polarizing plate 105 are arranged so as to be ina cross nicol state. Moreover, although not shown, the backlight and thelike are provided outside the fourth polarizing plate 106.

When a voltage is applied to the pair of electrodes 111 and 112 in aliquid crystal display device having such a structure, white display isperformed, which means an on state, as shown in FIG. 26A. Accordingly,light from the backlight can pass through the substrate over which oneof a pair of polarizing plates, which is stacked on the viewing side, isarranged displaced from a parallel nicol state; therefore, apredetermined image can be displayed.

By providing a color filter at that time, full-color display can beperformed. The color filter can be provided on either the firstsubstrate 101 side or the second substrate 102 side.

When a voltage is not applied between the pair of electrodes 111 and112, black display is performed, which means an off state, as shown inFIG. 26B. At that time, liquid crystal molecules are alignedhorizontally and are in a twisted state in a plane. As a result, lightfrom the backlight cannot pass through the substrate, which leads toblack display.

A known liquid crystal material may be used for the IPS mode.

Display with a higher contrast ratio can be achieved by applying a pairof stacked polarizing plates of the present invention to a liquidcrystal display device of the vertical electric field method in such away that one of the pair of stacked polarizing plates on the viewingside is arranged displaced from a parallel nicol state. The verticalelectric field method is suitable for a display device for a computerand a large-sized television which are used indoors.

When the present invention is applied to a liquid crystal display deviceof the horizontal electric field method, display with a wider viewingangle and a higher contrast ratio can be realized. The horizontalelectric field method is preferable for a portable display device.

FIGS. 27A and 27B are pattern diagrams each showing a liquid crystal ofan FLC (Ferroelectric Liquid Crystal) mode and an AFLC(Antiferroelectric Liquid Crystal) mode.

Similarly to FIGS. 23A and 23B, the first electrode 108 and the secondelectrode 109 are provided over the first substrate 101 and the secondsubstrate 102, respectively. In addition, an electrode on the sideopposite to the backlight, that is, the first electrode 108 on theviewing side is formed so as to have at least a light-transmittingproperty. The first polarizing plate 103 and the second polarizing plate104 are arranged displaced from a parallel nicol state. On the secondsubstrate 102 side, the third polarizing plate 105 and the fourthpolarizing plate 106 are arranged so as to be in a parallel nicol state.The first polarizing plate 103 and the third polarizing plate 105 arearranged so as to be in a cross nicol state.

When a voltage is applied to the first electrode 108 and the secondelectrode 109 (referred to as the vertical electric field method) in aliquid crystal display device having such a structure, white display isperformed as shown in FIG. 27A. At that time, liquid crystal moleculesare aligned horizontally and are in a twisted state in a plane.Accordingly, light from the backlight can pass through the substrateover which one of a pair of polarizing plates, which is stacked on theviewing side, is provided displaced from a parallel nicol state;therefore, a predetermined image can be displayed.

Meanwhile, when a voltage is not applied between the first electrode 108and the second electrode 109, black display is performed as shown inFIG. 27B. At this time, the liquid crystal molecules are alignedhorizontally. Then, light from the backlight cannot pass through thesubstrate, thereby performing black display.

By providing a color filter at that time, full-color display can beperformed. The color filter can be provided on either the firstsubstrate 101 side or the second substrate 102 side.

A known liquid crystal material may be used for the FLC mode and theAFLC mode.

Besides, the invention can be applied to a liquid crystal display deviceof a rotation mode, a scattering mode, or a birefringence mode, and adisplay device in which a polarizing plate is provided on each side of asubstrate.

This embodiment mode can be freely combined with the above embodimentmode.

Embodiment Mode 12

An electronic appliance of the present invention includes: a televisionset (also simply referred to as a TV or a television receiver), a camerasuch as a digital camera and a digital video camera, a mobile phone set(also simply referred to as a cellular phone set or a cellular phone), aportable information terminal such as a PDA, a portable game machine, amonitor for a computer, a computer, an audio reproducing device such asa car audio set, an image reproducing device provided with a recordingmedium such as a home-use game machine, and the like. Specific examplesthereof are described with reference to FIGS. 28A to 28F.

A portable information terminal shown in FIG. 28A includes a main body9201, a display portion 9202, and the like. The display device of theinvention can be applied to the display portion 9202. Thus, a portableinformation terminal with a high contrast ratio can be provided.

A digital video camera shown in FIG. 28B includes a display portion9701, a display portion 9702, and the like. The display device of theinvention can be applied to the display portion 9701. Thus, a digitalvideo camera with a high contrast ratio can be provided.

A cellular phone set shown in FIG. 28C includes a main body 9101, adisplay portion 9102, and the like. The display device of the inventioncan be applied to the display portion 9102. Thus, a cellular phone setwith a high contrast ratio can be provided.

A portable television set shown in FIG. 28D includes a main body 9301, adisplay portion 9302, and the like. The display device of the inventioncan be applied to the display portion 9302. Thus, a portable televisionset with a high contrast ratio can be provided. The display device ofthe invention can be applied to various types of television setsincluding a small-sized television incorporated in a portable terminalsuch as a cellular phone set, a medium-sized television which isportable, and a large-sized television (for example, 40 inches in sizeor more).

A portable computer shown in FIG. 28E includes a main body 9401, adisplay portion 9402, and the like. The display device of the inventioncan be applied to the display portion 9402. Thus, a portable computerwith a high contrast ratio can be provided.

A television set shown in FIG. 28F includes a main body 9501, a displayportion 9502, and the like. The display device of the invention can beapplied to the display portion 9502. Thus, a television set with a highcontrast ratio can be provided.

In this manner, an electronic appliance with a high contrast ratio canbe provided by using the display device of the present invention.

Embodiment 1

Embodiment 1 will show results of optical calculation with respect to aTN liquid crystal element having stacked polarizing plates.

First, a liquid crystal element as a target of the optical calculationwas formed as shown in FIG. 13. A polarizing plate 1, a polarizing plate2, a TN liquid crystal 1001, a polarizing plate 3, and a polarizingplate 4 were stacked in order from a backlight 1000. That is to say, twopolarizing plates which have been stacked were provided on each side ofthe TN liquid crystal in this liquid crystal element. The TN liquidcrystal has an anisotropy of dielectric constant Δε=5.2. Then, theliquid crystal element has a cell thickness of 4 μm. It is to be notedthat Chart 1 shows values of birefringence Δn of the TN liquid crystalat a wavelength of 546.1 nm. It is understood from Chart 1 that thebirefringence changes depending on temperature.

CHART 1 Temperature [° C.] Δn 20 0.099 25 0.097 40 0.092 60 0.083

As each of the polarizing plates, EG1425DU in the database of LCD MASTERwith its film thickness set to 180 μm was used. In such a liquid crystalelement, a rubbing direction was set perpendicular to an absorption axisof each polarizing plate, i.e., parallel to a transmission-axisdirection on the backlight side and a viewing side, so as to be in anormally white mode.

At this time, the absorption axes of the polarizing plate 1 and thepolarizing plate 2 provided on the backlight side were arranged at 135°to a reference line. Moreover, the absorption axis of the polarizingplate 3 provided on the viewing side was arranged at 45° to a referenceline, i.e., the polarizing plate 3 was arranged so as to be in a crossnicol state with respect to the polarizing plate 1 and the polarizingplate 3. Then, the angle of the absorption axis of the polarizing plate4 was gradually displaced from the state of 45° to the reference line.That is to say, the absorption axis of the polarizing plate 4 wasgradually displaced from that of the polarizing plate 3. The opticalcalculation was carried out in this state.

FIG. 14 shows a result of a contrast ratio with respect to the anglebetween the absorption axis of the polarizing plate 4 and the referenceline. The optical calculation was carried out with the angle between theabsorption axis and the reference line ranging from 35° to 55°. Thecontrast ratio is calculated from the relative ratio between theluminance of white display and that of black display. In order toperform black display, a voltage of 4.5 V (ON voltage) was applied tothe liquid crystal element; on the other hand, in order to perform whitedisplay, a voltage of 1.7 V (OFF voltage) was applied to the liquidcrystal element. Then, the contrast ratio of the liquid crystal elementwas measured with the temperature of the TN liquid crystal set to 20°C., 25° C., 40° C., and 60° C.

It is understood from FIG. 14 that the contrast ratio differs dependingon the temperature of the TN liquid crystal. For example, it is when theangle between the absorption axis of the polarizing plate 4 and thereference line is 41.5° that the contrast ratio is the maximum at 20° C.Moreover, it is when the angle between the absorption axis of thepolarizing plate 4 and the reference line is 42.5° that the contrastratio is the maximum at 60° C. It is understood from FIG. 14 that theangle between the absorption axis of the polarizing plate 4 and thereference line is 38° to 45°, that is, the angle between the absorptionaxis of the polarizing plate 4 and the absorption axis of the polarizingplate 3 is within 7°, preferably within 5°, in order to increase thecontrast ratio so as to be higher than contrast ratio when the anglebetween the absorption axis of the polarizing plate 4 and the referenceline is 45°.

It is understood that the contrast ratio is increased by displacing thestacked polarizing plates in this manner Moreover, it is understood thatwhen the stacked polarizing plates are displaced, the contrast ratioshows temperature dependency with respect to the angle of the absorptionaxis of the polarizing plate 4 at which the contrast ratio is themaximum.

Embodiment 2

Embodiment 2 shows results of optical calculation on temperaturedependency with respect to the contrast ratio. Here, description is madeof a method for fixing the contrast ratio without depending on thetemperature while the stacked polarizing plates are displaced.

FIG. 15 shows transmittance at white display with respect to an appliedvoltage when the angle between the reference line and the absorptionaxis of the polarizing plate 4 shown in FIG. 13 is 41.5°. It isunderstood that the transmittance at white display gets lower with theincrease in temperature of the TN liquid crystal. In order to fix thecontrast ratio with respect to the temperature of the TN liquid crystal,the transmittance at white display may be fixed. For example, thetransmittance at white display is fixed at 0.22.

Chart 2 shows specific values of a voltage applied to the liquid crystalelement for performing white display with respect to each temperature ofthe TN liquid crystal.

CHART 2 Temperature [° C.] Applied Voltage [V] 20 1.70 25 1.67 40 1.5960 1.28

Next, FIG. 16 shows transmittance at black display with respect to anapplied voltage when the angle between the reference line and theabsorption axis of the polarizing plate 4 is 41.5°. It is understoodthat the transmittance at black display gets lower with the increase intemperature of the TN liquid crystal. In order to fix the contrast ratiowith respect to the temperature of the TN liquid crystal, thetransmittance at black display may be fixed. For example, thetransmittance at black display is fixed at 1.17×10⁻⁵.

Chart 3 shows specific values of a voltage applied to the liquid crystalelement for performing black display with respect to each temperature ofthe TN liquid crystal.

CHART 3 Temperature [° C.] Applied Voltage [V] 20 4.50 25 4.51 40 4.5360 4.58

Next, FIG. 17 shows results of plotting a contrast ratio with respect tothe temperature of the TN liquid crystal. Also in this measurement, thepolarizing plate 4 was provided with its absorption axis set at 41.5° tothe reference line, i.e., the polarizing plate 4 was arranged displaced,so as to obtain a high contrast ratio. Moreover, as shown in Charts 2and 3, a voltage applied to the liquid crystal element was controlled sothat the transmittance at white display and the transmittance at blackdisplay were fixed with respect to the temperature of the TN liquidcrystal. As a comparative example, a result of a comparative elementwhich is arranged so that the angle between the absorption axis of thepolarizing plate 4 and the reference line is 45° is shown. In thecomparative element, regardless of the temperature, a voltage of 0 V wasapplied to perform black display and a voltage of 5 V was applied toperform white display.

It is understood from FIG. 17 that a high contrast ratio can be obtainedin the liquid crystal element of the present invention and a fixedcontrast ratio can be obtained at temperatures of the TN liquid crystalranging from 20° C. to 60° C. On the other hand, it is understood thatthe comparative element has a low contrast ratio and the contrast ratiothereof changes depending on the temperature of the TN liquid crystal.

Thus, it is understood that the liquid crystal element of the presentinvention has a high contrast ratio. Although the contrast ratio changesdepending on the temperature of the TN liquid crystal, it is understoodthat drive voltage is desirably controlled so as to maintain a fixedcontrast ratio. In order to control the drive voltage, an element fordetecting the transmittance may be provided in the display device andthe drive voltage may be controlled based on a detection result. As theelement for detecting the transmittance, a photosensor including an ICchip can be used. In the display device, an element for detectingtemperature may be provided and the drive voltage may be controlledbased on a detection result and the change in a contrast ratio withrespect to the temperature of the liquid crystal element. As the elementfor detecting the temperature, a temperature sensor including an IC chipcan be used. In this case, the element for detecting the transmittanceand the element for detecting the temperature are preferably arranged soas to be hidden in the housing of the display device.

Embodiment 3

Embodiment 3 will show results of optical calculation with respect to aVA liquid crystal element having stacked polarizing plates.

First, as shown in FIG. 18, a liquid crystal element as a target of theoptical calculation was formed. A polarizing plate 1, a polarizing plate2, a retardation plate 1002, a VA liquid crystal 1003, a retardationplate 1004, a polarizing plate 3, and a polarizing plate 4 were stackedin order from a backlight 1000. That is to say, a retardation plate andtwo polarizing plates which have been stacked are provided on each sideof the VA liquid crystal in this liquid crystal element. In thisembodiment, the retardation plate was inserted in order to improve aviewing angle that affects a polarizing state of incident light. The VAliquid crystal has an anisotropy of dielectric constant Δε=−4.3. Then,the liquid crystal element has a cell thickness of 2.44 μm. It is to benoted that Chart 4 shows values of birefringence of the VA liquidcrystal at a wavelength of 546.1 nm. It is understood from Chart 4 thatthe birefringence changes depending on temperature.

CHART 4 Temperature [° C.] Δn 20 0.1300 40 0.1208 50 0.1155 60 0.1088

As each of the polarizing plates, EG1425DU in the database of LCD MASTERwith its film thickness set to 180 μm was used. In such a liquid crystalelement, the pretilt angle is set to 88°.

In this case, the polarizing plate 1 and the polarizing plate 2 on thebacklight side were arranged so that the absorption axis of each of thepolarizing plates 1 and 2 has an angle of 45° to a reference line.Moreover, the polarizing plate 3 was provided on the viewing side sothat the absorption axis of the polarizing plate 3 has an angle of 135°to the reference line, i.e., the polarizing plate 3 was arranged in across nicol state with respect to the polarizing plate 1 and thepolarizing plate 3. Then, the angle of the absorption axis of thepolarizing plate 4 was gradually displaced from the state of 135° to thereference line. The optical calculation was carried out in this state.

FIG. 19 shows a result of a contrast ratio with respect to the anglebetween the absorption axis of the polarizing plate 4 and the referenceline. The optical calculation was carried out with the angle between theabsorption axis and the reference line ranging from 125° to 145°. Inorder to perform white display, a voltage of 6.5 V (ON voltage) wasapplied to the liquid crystal; on the other hand, in order to performblack display, a voltage of 0.6 V (OFF voltage) was applied to theliquid crystal. Then, the contrast ratio of the liquid crystal elementwas measured with the temperature of the VA liquid crystal set to 20°C., 25° C., 40° C., and 60° C.

It is understood from FIG. 19 that the contrast ratio differs dependingon the temperature of the VA liquid crystal. For example, it is when theangle between the absorption axis of the polarizing plate 4 and thereference line is 139.5° that the contrast ratio is the maximum at 20°C. Moreover, it is when the angle between the absorption axis of thepolarizing plate 4 and the reference line is 139° that the contrastratio is the maximum at 60° C. It is understood from FIG. 19 that theangle between the absorption axis of the polarizing plate 4 and thereference line is 135° to 144°, that is, the angle between theabsorption axis of the polarizing plate 4 and the absorption axis of thepolarizing plate 3 is within 9°, preferably within 7°, in order toincrease the contrast ratio so as to be higher than contrast ratio whenthe angle between the absorption axis of the polarizing plate 4 and thereference line is 135°.

It is understood that the contrast ratio is increased by displacingabsorption axes of the stacked polarizing plates in this mannerMoreover, it is understood that when the absorption axes of the stackedpolarizing plates are displaced, the contrast ratio shows temperaturedependency with respect to the angle of the absorption axis of thepolarizing plate 4 at which the contrast ratio is the maximum.

Embodiment 4

Embodiment 4 shows results of optical calculation on temperaturedependency with respect to a contrast ratio. Here, description is madeof a method for fixing the contrast ratio without depending on thetemperature while the stacked polarizing plates are displaced.

FIG. 20 shows transmittance at white display with respect to an appliedvoltage when the angle between the reference line and the absorptionaxis of the polarizing plate 4 shown in FIG. 18 is 139°. It isunderstood that the transmittance at white display gets lower with theincrease in temperature of the VA liquid crystal. In order to fix thecontrast ratio with respect to the temperature of the VA liquid crystal,the transmittance at white display may be fixed. For example, thetransmittance at white display may be fixed at 0.25.

Chart 5 shows specific values of a voltage applied to perform whitedisplay at each temperature of the VA liquid crystal.

CHART 5 Temperature [° C.] Applied Voltage [V] 20 4.4 25 4.9 40 5.4 606.5

Next, FIG. 21 shows transmittance at black display with respect to anapplied voltage when the angle between the absorption axis of thepolarizing plate 4 and the reference line is 139°. It is understood thatthe transmittance at black display gets lower with the increase intemperature of the VA liquid crystal. In order to fix the contrast ratiowith respect to the temperature of the VA liquid crystal, thetransmittance at black display may be fixed. For example, thetransmittance at black display may be fixed at 8.79×10⁻⁷.

Chart 6 shows specific values of a voltage applied to perform blackdisplay at each temperature of the VA liquid crystal.

CHART 6 Temperature [° C.] Applied Voltage [V] 20 0   25 0.4 40 0.5 600.6

Next, FIG. 22 shows results of plotting a contrast ratio with respect tothe temperature of the VA liquid crystal. Also in this measurement, thepolarizing plate 4 was provided with its absorption axis set at 139° tothe reference line, i.e., the polarizing plate 4 was arranged displaced,so as to obtain a high contrast ratio. Moreover, as shown in Charts 5and 6, the voltage applied to the liquid crystal element was controlledso that the transmittance at white display and the transmittance atblack display were fixed with respect to the temperature of the VAliquid crystal. As a comparative example, a result of a comparativeelement which is arranged so that the angle between the absorption axisof the polarizing plate 4 and the reference line is 135° is shown. Inthe comparative element, regardless of the temperature, a voltage of 0 Vwas applied to perform black display and a voltage of 5 V was applied toperform white display.

Chart 7 shows structures of the liquid crystal element and thecomparative element.

CHART 7 Liquid crystal element of the present invention polarizing plate4 displacement absorption axis from 135° to 139° polarizing plate 3absorption axis 135° retardation plate — liquid crystal controlliingvoltage in accordance with charts 5, 6 retardation plate — polarizingplate 2 absorption axis 45° polarizing plate 1 absorption axis 45°Liquid crystal element of the comparative example polarizing plate 4absorption axis 135° polarizing plate 3 absorption axis 135° retardationplate — liquid crystal fixed voltage (0V, 5V) retardation plate —polarizing plate 2 absorption axis 45° polarizing plate 1 absorptionaxis 45°

It is understood from FIG. 22 that a high contrast ratio can be obtainedin the liquid crystal element of the present invention and a fixedcontrast ratio can be obtained at temperatures of the VA liquid crystalranging from 20° C. to 60° C. Although the contrast ratio is somewhathigh at 60° C., this can be solved by specifically controlling a voltagewhen the transmittance at black display is controlled. On the otherhand, it is understood that the comparative element has a low contrastratio and the contrast ratio thereof changes depending on thetemperature of the VA liquid crystal.

Thus, it is understood that the liquid crystal element of the presentinvention has a high contrast ratio. Although the contrast ratio changesdepending on the temperature of the VA liquid crystal, it is understoodthat drive voltage is desirably controlled so as to maintain a fixedcontrast ratio. In order to control the drive voltage, an element fordetecting the transmittance may be provided in the display device andthe drive voltage may be controlled based on a detection result. As theelement for detecting the transmittance, a photosensor including an ICchip can be used. In the display device, an element for detectingtemperature may be provided and the drive voltage may be controlledbased on a detection result and the change in a contrast ratio withrespect to the temperature of the liquid crystal element. As the elementfor detecting the temperature, a temperature sensor including an IC chipcan be used. In this case, the element for detecting the transmittanceand the element for detecting the temperature are preferably arranged soas to be hidden in the housing of the display device.

This application is based on Japanese Patent Application serial no.2005-380220 filed in Japan Patent Office on Dec. 28, 2005, the entirecontents of which are hereby incorporated by reference.

1. A display device comprising: a first light-transmitting substrate; asecond light-transmitting substrate; a display element sandwichedbetween the first light-transmitting substrate and the secondlight-transmitting substrate; a first polarizing plate having a firsttransmission axis and a second polarizing plate having a secondtransmission axis; and a third polarizing plate having a thirdtransmission axis and a fourth polarizing plate having a fourthtransmission axis, wherein the first polarizing plate and the secondpolarizing plate are stacked outside the first light-transmittingsubstrate, wherein the third polarizing plate and the fourth polarizingplate are stacked outside the second light-transmitting substrate,wherein the second transmission axis is displaced so as to correspond toa minor-axis direction of an ellipse of elliptically-polarized lightemitted from the first polarizing plate, and wherein the thirdtransmission axis and the fourth transmission axis are in a parallelnicol state.
 2. The display device according to claim 1, wherein thefirst transmission axis and the third transmission axis are in a crossnicol state.
 3. The display device according to claim 1, wherein thefirst transmission axis and the fourth transmission axis are displacedfrom a cross nicol state.
 4. The display device according to claim 1,wherein the first polarizing plate and the second polarizing plate arearranged on a viewing side.
 5. A display device comprising: a firstlight-transmitting substrate; a second light-transmitting substrate; adisplay element sandwiched between the first light-transmittingsubstrate and the second light-transmitting substrate; a firstpolarizing plate having a first transmission axis and a secondpolarizing plate having a second transmission axis; a third polarizingplate having a third transmission axis and a fourth polarizing platehaving a fourth transmission axis; a first retardation plate between thefirst polarizing plate and the first light-transmitting substrate; and asecond retardation plate between the third polarizing plate and thesecond light-transmitting substrate, wherein the first polarizing plateand the second polarizing plate are stacked outside the firstlight-transmitting substrate, wherein the third polarizing plate and thefourth polarizing plate are stacked outside the secondlight-transmitting substrate, wherein the second transmission axis isdisplaced so as to correspond to a minor-axis direction of an ellipse ofelliptically-polarized light emitted from the first polarizing plate,and wherein the third transmission axis and the fourth transmission axisare in a parallel nicol state.
 6. The display device according to claim5, wherein the first transmission axis and the third transmission axisare in a cross nicol state.
 7. The display device according to claim 5,wherein the first transmission axis and the fourth transmission axis aredisplaced from a cross nicol state.
 8. The display device according toclaim 5, wherein the first polarizing plate and the second polarizingplate are arranged on a viewing side.
 9. The display device according toclaim 1, wherein each of the first polarizing plate, the secondpolarizing plate, the third polarizing plate and the fourth polarizingplate comprises TAC (triacetylcellulose), a mixed layer of PVA(polyvinyl alcohol) and iodine, and TAC.
 10. The display deviceaccording to claim 1, wherein each of the first polarizing plate, thesecond polarizing plate, the third polarizing plate and the fourthpolarizing plate comprises an inorganic material.
 11. The display deviceaccording to claim 5, wherein each of the first polarizing plate, thesecond polarizing plate, the third polarizing plate and the fourthpolarizing plate comprises TAC (triacetylcellulose), a mixed layer ofPVA (polyvinyl alcohol) and iodine, and TAC.
 12. The display deviceaccording to claim 5, wherein each of the first polarizing plate, thesecond polarizing plate, the third polarizing plate and the fourthpolarizing plate comprises an inorganic material.
 13. An electronicappliance having the display device according to claim 1, wherein theelectronic appliance is one selected from the group consisting of atelevision set, a camera such as a digital camera and a digital videocamera, a mobile phone set, a portable information terminal, a portablegame machine, a monitor for a computer, a computer, an audio reproducingdevice, and an image reproducing device provided with a recordingmedium.
 14. An electronic appliance having the display device accordingto claim 5, wherein the electronic appliance is one selected from thegroup consisting of a television set, a camera such as a digital cameraand a digital video camera, a mobile phone set, a portable informationterminal, a portable game machine, a monitor for a computer, a computer,an audio reproducing device, and an image reproducing device providedwith a recording medium.
 15. The display device according to claim 1,wherein the display element is a liquid crystal element.
 16. The displaydevice according to claim 5, wherein the display element is a liquidcrystal element.
 17. The display device according to claim 1, wherein anangle between the first transmission axis and the second transmissionaxis is within 7°.
 18. The display device according to claim 5, whereinan angle between the first transmission axis and the second transmissionaxis is within 7°.